Clamshell structures for affecting fusion of pipes are well known in the art being disclosed in various documents such as WO80102124 wherein overlapping plastic pipes have a ferromagnetic material located in the overlap region which is excited by a magnetic field carried in a clamshell having a coil therein.
U.S. Pat. No. 4,914,267 discloses a clamshell heater for fusing solder to effect a solder joint between wires.
There are numerous types of clamshell coils or heaters but each is tailored to a specific device, a pipe of a given dimension or other object of given structure and/or dimensions. Thus there must be a clamshell for each such size or shape of structure to be heated or fused, a costly approach and one which becomes unwieldy as the pipes or other structures become large.
A further problem is that it is difficult to achieve close fitting clamshell heaters with a low Q so that the prior devices are relatively inefficient, the voltages are high and a series resonant capacitor is required in all instances. The result of all this is that the clamshell is unwieldy, costly and produces high voltages that must be handled with great care.
A close fitting solenoid coil can provide lower Q's than the clamshell devices but it requires both mechanical and electrical connections and high voltages since the coupling coefficients are not more than 0.6.
The current approaches to fusion coupling do not provide common elements for pipes, saddles, tees or patches so that a special tool is required for each.